Aircraft: COMMERCIAL FIXED WING
Phase of flight: Taxi
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Other / Unknown

We started loading our flight 1 hr before its departure. I was told by the Lead; that he was going to be the push back and my partner was going to do the card. I went about loading mail and bags as well as picking up bags as the Lead directed. As we were loading the plane; the Lead changed his mind and asked me to do the push back because [an employee] did not show up to our flight. Usually I try to have a push back tug hooked up and ready to push the plane prior to loading the plane; but I felt like I had to rush the hookup process because I was told to hookup in the middle of our loading. We also had a crew member that did not show up to our flight so we were short man power. I proceeded to retrieve a push back tug and tow bar from [another gate] and hook it up by myself to our flight. After hooking up the tow bar; I continued to help with retrieving and loading bags. As the departure time was getting closer; I radioed the flight deck for permission to disconnect AC and power cord. After receiving the go ahead; I disconnected and stowed the AC and power cord. I did my walk around the plane scanning for anything of concern. I directed CS (Customer Service) to retract the jet bridge. I observed that the envelope was clear of any equipment and our crew was ready to wing walk. I got in the push back tug and radioed the flight deck that we were ready to push. Flight deck released the brakes and gave clearance to push. I began to push for about 15 feet when the tow bar popped off and separated from the plane. I notified the flight deck that there was a breakaway and the pilot replied that he would set brakes gently as the plane rolled slowly for about 6-8 feet. I immediately checked on my wing walkers as well as the detached tow bar and observed there was no bypass pin. I knew immediately that I had forgotten to insert the bypass pin. I retrieved the bypass pin and inserted it and notified the flight deck that I had forgot to put in the bypass pin and we were dealing with the situation and to standby. The pilot asked for maintenance to check for any damages and would standby as he made his report. I told the lead what happened and he told me to get another tow bar while maintenance checked for damages and cleared the plane for departure. By this time the supervisors had been notified and were at the gate. Thankfully no one was hurt and maintenance found there was no damage to the plane. The Lead was asked to push back and I wing walked. The plane departed about 10-15 minutes after its scheduled departure. I went with the supervisor to turn in my box and went to the supervisors' office to discuss the incident and take a breathalyser and drug test. A shop steward came to help me during this process. I turned in my airport badge and employee badge and was told to go home and wait until further notice which could be up to a week. A Ramp Agent installed a tow bar between loading baggage tasks but failed to install the nose gear steering bypass pin. The tow bar separated from the nose wheel then rolled 6 to 8 feet after the agent notified the crew. Maintenance found no damage so connected a new tow bar to resume the push.